1. Field of the Invention
This invention relates to modulating polarized light by transmitting the polarized light through at least one liquid crystal cell containing a thin layer of nematic liquid crystal composition having positive dielectric anisotropy.
2. Description of the Prior Art
Liquid crystal cells containing a layer of nematic liquid crystal composition between a pair of parallel transparent plates are employed in a variety of optical installations. Such devices are used principally in digital display devices.
In my copending application Ser. No. 121,071 aforesaid, an improved liquid crystal cell is described wherein a conductive transparent film is provided on each side of the transparent flat plates which confine the liquid crystal composition and an electrical bias voltage, AC or DC, is applied to the two thin films to permit the liquid crystal composition to respond rapidly to additional electrical voltages applied across the two conductive coatings.
It is also known that thin layers of liquid crystal composition will bring about a phase shift in a beam of polarized light which is transmitted through the liquid crystal composition. Heretofore, the devices have been employed as light shutters which block the polarized light in the regions where an electrical field is established across the liquid crystal composition. Typical turn-off times of 250-300 milliseconds are common with existing liquid crystal light shutters which employ nematic liquid crystals. Such response time is much too large to permit the use of such devices in high speed communication.